RIO DE JANEIRO—Top officials from Rio de Janeiro said Friday they want elite federal police sent to the city to help quell a wave of violence in so-called “pacified” slums.

The announcement came hours after suspected drug gang members attacked three police shantytown outposts, injuring three officers and burning one of the metal shipping containers they use as offices in slums. The violence hit an area near the slum that Pope Francis visited during his trip to Brazil last year.

The attacks raise concerns about an ambitious security program that began in 2008, in part to secure the city ahead of this year’s World Cup and the 2016 Olympics. The effort sees police and at times army troops invade slums, push out drug gangs and set up permanent posts in areas where traffickers held sway for decades.

Jose Beltrame, Rio’s top security official and the architect of the pacification program, said the recent attacks on police were ordered by imprisoned drug gang leaders in an effort to disrupt expansion of the program, which would further restrict the area held by the gangs.

Rio Gov. Sergio Cabral was set to meet with President Dilma Rousseff in Brasilia on Friday to request the help of federal police. He didn’t say what other assistance he may request, or how many federal officers he would like.

The governor said the violence is “an attempt by criminals to weaken the successful pacification program, which has retaken territory that’s historically been occupied by gangs and returned it to government control.”

Since the inception of the security program, police have created 37 permanent “pacification units” that they say covers an area with a population of 1.5 million. Murders are down in those areas and the number of shootouts has dropped.

Yet residents of those slums often have accused police of heavy-handed tactics.

More than 20 police who patrolled Rio’s largest slum, Rocinha, are facing charges for the disappearance last year of 42-year-old construction worker Amarildo de Souza. Police investigators say he died while being tortured by officers who were seeking information about where a gang was hiding drugs and guns. His body has yet to be found.